The present invention relates to systems and methods used in the manufacture of carbon nanostructure-laden materials, and more specifically to measuring the resistance of carbon nanostructure-laden materials during their manufacture.
High-performance materials incorporating carbon nanostructures (CNSs) are becoming increasingly important industrially. CNSs may impart desirable properties to composites, for example, such as enhanced mechanical strength, and thermal and electrical conductivity. The small diameter and robust individual carbon-carbon bonds of carbon nanotubes (CNTs), in particular, provide stiffness, strength, and thermal conductivity which exceed most known natural and synthetic materials.
In order to harness these properties, a continuing challenge has been to reliably incorporate CNTs and other CNSs into various structures, preferably in a controlled and ordered fashion. While the preparation of CNTs, in particular, has been successfully scaled up, employing loose CNTs has been problematic due, at least in part, to their tendency to agglomerate. Moreover, when combined in a typical matrix material, CNT loading can be severely limited by the concomitant increases in viscosity, ultimately putting an upper limit on the amount of CNTs that can be placed in the matrix material. As a consequence, there has been increased interest in the preparation of CNTs on various substrates as scaffolds to pre-organize the CNTs and to allow access to higher CNT loadings.
As the means for synthesizing CNSs, such as CNTs, on a variety of substrates begins to mature and industrial scale up begins to take hold, it will be beneficial to put into place measures to ensure quality control of the materials being prepared. Although there are means for analyzing CNT loading of a substrate, there are no real-time quantitative evaluations adapted for in-line use. CNT loading evaluation methods include, for example, thermogravimetric analysis employing CNT burnoff, measuring mass per unit length, and the use of scanning electron microscope (SEM) techniques. Currently, such evaluations are done “offline,” that is, after the material is prepared and via random sampling.
Thermogravimetric analysis employs random sampling and destroys the very substrate being prepared. Measuring mass per unit length provides only an averaged evaluation of loading over an entire stretch of substrate and is difficult to employ real-time and fails to identify regions that may not be up to quality standards. Similarly, SEM techniques are inadequate for large scale quality control assurance, because only random samplings of the CNS-laden substrate are evaluated. Each of these post synthesis analyses may be inadequate to detect problems that may occur, for example, during a long synthesis run. Moreover, the use of CNS-laden materials that may have undesirable imperfections, such as regions of poor CNS coverage, may be catastrophic under high stress conditions of certain downstream applications.